Strains of the genus Lactobacillus are normal inhabitants of the gastrointestinal tract of many animal species. In pigs, lactobacilli are one of the principal bacterial groups in the proximal region of the digestive tract (Barrow, P. A., R. Fuller, and N. J. Newport. 1977. Inft, Immun. 18: 586-595). Their beneficial role in the intestinal tract has been attributed to their ability to survive the digestive process, attach to the epithelial lining of the intestinal tract, produce lactic acid and other antimicrobial compounds, and prevent the colonization of pathogens via competitive exclusion (Savage, D. C. 1987. Factors affecting the biocontrol of bacterial pathogens in the intestine. Food Technol. 41: 82-87).
Many allogenic and autogenic factors influence the microbial population of the gastrointestinal tract (Savage, D. C. 1989. Rev. sci. tech Off. int. Epiz. 8: 259-273). Allogenic factors such as alterations in the diet and environment along with maturation of the host are major influences on the succession of Lactobacillus strains in the gastrointestinal tract of pigs during the post-weaning phase. Although it has been well documented that these changes may have severe effects on the host, little is understood about the distribution and diversity of lactobacilli species during this period.
Current industry practices to improve health and, more specifically, reduce the levels of coliforms and E. coli within the gastrointestinal tract of pigs generally include feeding antibiotics at subtherapeutic levels. However, the practice of feeding antibiotics to livestock has raised concerns about increasing the antibiotic resistance of microbial pathogens in the food supply.
Another approach to improving the health of animals is to alter the inhabitants of their gastrointestinal tract. Altering the inhabitants of the gastrointestinal tract of animals has been attempted by feeding direct-fed microbials to animals. The efficacy of single or multiple strains of Lactobacillus commonly used in commercial direct-fed microbials has been and continues to be debated. This debate is primarily due to inconsistent performance of previous direct-fed microbials. This inconsistency may be due to the fact that many commercial direct-fed microbials are composed of Lactobacillus strains commonly used as silage inoculants or cheese starter cultures. These strains may be effective to inoculate silage or to convert milk into cheese, but have no proven efficacy as direct fed microbials for animal feeding. While the “one strain for all products” approach may be an economical method for the commercial fermentation industry, this does not provide the best strains for each application.
In view of the foregoing, it would be desirable to provide a direct-fed microbial that reduces the levels of coliforms and E. coli within the gastrointestinal tract of pigs. In particular, it would be desirable to provide a direct-fed microbial that provides a healthier intestinal microflora during the weaning transition period in pigs.